This project is designed to investigate the development of verbal communication in school-age persons with mild forms of mental retardation. The project is based on a model in which any act of communication is thought to involve two goals: (a) the exchange of information about the participants' intentions, beliefs, and desires and (b) the maintenance of appropriate social relationships among the participants. The project has four specific aims. The first aim is to determine the extent and nature of the problems that persons with mental retardation experience in achieving the goals of communication. To this end, eight studies will be conducted. Four focus on the task of establishing the referents of messages, which is an important component of the goal of exchanging information. The remaining studies focus on being polite when making and responding to requests, which is an important component of the goal of maintaining appropriate social relationships. In each study, the performance of persons with mental retardation on a communication task will be compared to that of nondisabled children matched to them on nonverbal MA. The second aim is to provide data on the ways in which achieving the goals of communication is constrained by skills in cognition (i.e., problem solving, memory, factual knowledge), social cognition (i.e., perspective taking, knowledge of social status), and linguistic competence (i.e., syntax and semantics). To meet this aim, the relation between performance on each communication task and measures of linguistic, cognitive, and social-cognitive competence will be examined through multiple regression analyses. The third aim is to test the hypothesis that because many persons with mental retardation produce speech low in intelligibility, their communicative performance often is based more on a desire to avoid talking than on a consideration of how best to achieve the goals of communication. This aim will be met by examining the relation between the intelligibility of the speech produced by the subjects with mental retardation and their performance on each of the communication tasks. The fourth aim is to provide data relevant to the hypothesis that the parents of persons with mental retardation interact with their children in ways that are less than optimal for the development of the latter's communication skills. To meet this aim, interactions between parents and their children will be examined for the occurrence of parental behaviors known to affect the communicative development of nondisabled children.